000 AXNT20 KNHC 212353 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 753 PM EDT Thu Jun 21 2018 Tropical Weather Discussion for North America, Central America Gulf of Mexico, Caribbean Sea, northern sections of South America, and Atlantic Ocean to the African coast from the Equator to 32N. The following information is based on satellite imagery, weather observations, radar and meteorological analysis. Based on 1800 UTC surface analysis and satellite imagery through 2300 UTC. ...TROPICAL WAVES... The axis of a tropical wave is near 26W from 03N-12N, moving W at 20 kt. Abundant cloudiness surrounds the wave's axis but convection is limited. The axis of a tropical wave is near 35W from 3N-11N, moving W at 20 kt. Scattered showers are noted from 05N to 08N between 30W and 36W. The axis of a tropical wave is near 44W from 3N-11N, moving W at about 15 knots. Scattered moderate convection is noted from 03N to 08N between 40W and 47W. The axis of a tropical wave is near 62W from 6N-17N, moving W at about 10 knots. Scattered moderate convection associated to this wave is affecting much of the Windward Islands. The axis of a tropical wave is near 73W from northern Colombia to western Hispaniola. Moisture associated to this tropical wave is supporting scattered showers and isolated thunderstorms across Hispaniola. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the coastal sections of Guinea near 10N13W to 05.5N30W. The ITCZ continues from 05.5N30W to 05N34W to 05N43W to 05N52W. Outside of the convection associated with the tropical waves, isolated moderate convection is from 04N to 08N between 55W and 58W. ...DISCUSSION... GULF OF MEXICO... A 1009 mb low pressure centered along the Texas/NE Mexico border near 26.5N99W continues to produce a large area of showers with embedded tstms over the western Gulf coast and NE Mexico, particularly over the states of Nuevo Leon and Tamaulipas, where heavy rain has been reported. This slow moving system will continue to generate rounds of rainfall across the western Gulf coast from Texas to western Louisiana today. Flooding of low lying and poor drainage areas will be possible. Winds and seas in the NW Gulf will diminish further today as the low weakens. A broad ridge will persist over the eastern Gulf, and support light winds and seas less than 3 ft east of 88W through the upcoming weekend. A surface trough will develop in the Yucatan Peninsula each afternoon, then move westward across the SW Gulf during the overnight hours, accompanied by fresh to occasionally strong east to southeast winds. CARIBBEAN SEA... A tropical wave is moving across the central Caribbean. Another tropical wave is moving into the eastern Caribbean. See Tropical Waves section for details. Expect increasing showers and isolated thunderstorms in association with the passage of these tropical waves. High pressure N of area is forecast to strengthen over the next couple of days while moving westward. As a result, the trade winds over the south-central Caribbean will strengthen and expand in areal coverage across the basin through early next week. Winds could reach near gale force along the coast of Colombia by Sun night. Fresh to strong winds will affect the Gulf of Honduras each night beginning tonight through Mon night. An upper-level trough extends from a cyclonic circulation located over the western Atlantic near 27N67W to another cyclonic circulation over the NW Caribbean and the Yucatan Peninsula. A diffluent pattern aloft between this trough and an anticyclonic circulation over the south-central Caribbean is helping to support scattered showers and tstms across the Caribbean waters from 15N- 20N between the tropical wave along 73W and 85W. As of 2100 UTC, a trough, surface reflection of the upper-level low is analyzed over the NW Caribbean, and extends from 20N86W to the Gulf of Honduras. Abundant tropical moisture will persist across the NW Caribbean and the Yucatan Peninsula on Fri. ATLANTIC OCEAN... An upper-level trough extends from a cyclonic circulation centered near 27N67W to eastern Cuba. Scattered showers and tstms are noted on the SE semicircle of the low affecting mainly the waters from 21N to 27N between 60W and 70W. High pressure of 1029 mb centered near 33N34W extends a ridge westward across the forecast area. Fresh trades are noted along the southern periphery of the ridge, but mainly between 40W-70W. This high pressure will slowly shift westward through Sat night, then remain nearly stationary near 30N55W through Tue. The tightening pressure gradient that results over the central Atlantic will support fresh to strong trade winds and seas of 8-10 ft E of the Lesser Antilles to about 45W by early Sat morning. These marine conditions will persist on Sun. The Saharan Air Layer (SAL) from CIMSS and visible satellite imagery indicate the presence of African dust between the west coast of Africa and the Lesser Antilles, more concentrated E of 50W. For additional information please visit http://www.hurricanes.gov/marine $$ AL/GR